Deep eutectic solvent-based liquid-phase microextraction coupled with reversed-phase high-performance liquid chromatography for determination of α-, β-, γ-, and δ-tocopherol in edible oils

For simultaneous analysis of four fat-soluble tocopherols (alpha-, beta-, gamma-, and delta-) in edible oils, an efficient and green method using deep eutectic solvent-based liquid-phase microextraction (DES-LPME) coupled with reversed-phase high-performance liquid chromatography (RP-HPLC) was developed. The DESs formed by different quaternary ammonium salts and ethanol were used as the extractants. Tetrabutylammonium chloride (TBAC)-ethanol DES at a molar ratio of 1:2 achieved the best extraction efficiency. Under the optimized conditions, the detection limits were in the range of 2.1-3.0 ng mL(-1). The intra-day and inter-day repeatability were in the ranges of 3.9-5.3% and 4.8-7.1%, respectively, and the recoveries for the real samples varied from 80.7% to 105.4%. The developed method was successfully employed for the determination of all four tocopherol homologues with an RP-HPLC system containing a COSMOSIL pi-NAP column in five edible oils collected locally.

Automated summary

An efficient and green method using DES-LPME coupled with RP-HPLC was developed for simultaneous analysis of four fat-soluble tocopherols in edible oils. The method showed good extraction efficiency, low detection limits, and satisfactory repeatability and recovery rates for real samples. This method has practical application prospects for the determination of tocopherols in edible oils.